1. Field of the Invention
The invention is directed to a torsional vibration damper for use with a motor vehicle clutch with a drive side transmission element connected with a driven side transmission element via a planetary gear set.
2. Description of the Related Art
A prior art torsional vibration damper with a drive-side transmission element which engages with a driven-side transmission element via a planetary gear set is disclosed in German reference DE 44 44 196 A1, wherein a flywheel is associated with each of the two transmission elements. The planetary gear set includes planet wheels rotatably mounted on planet carriers and engage with other toothed wheels of the planetary gear set such, for example, as a ring gear. The latter is enclosed by damping elements in the form of springs which act in the circumferential direction and which are supported at one end at one of the transmission elements by the ring gear and are supported at the other end at the other transmission element by control means.
The toothed wheels of planetary gear sets in torsional vibration dampers of this kind are usually manufactured from steel. Accordingly, while these toothed wheels may be manufactured advantageously, the problem of extensive wear of the gear teeth or toothing occurs insofar as at least a portion of the toothed wheels is not arranged in a grease chamber which is at least partially filled with viscous medium as is described in the German reference. On the one hand, this viscous medium brings about a speed-proportional damping due to its displacement during movements of the transmission elements and toothed wheels. On the other hand, it also serves to lubricate the toothing and accordingly reduces the toothing wear mentioned above. A problem with this prior art device is that to effect the lubrication mentioned above, the amount of viscous medium in the grease chamber must be higher than would be required to achieve the speed-proportional damping alone. The reason for this is that the viscous medium must still reach at least the toothing region radially outside of the dedendum or root circle of the planet wheels even when it has been distributed in a ring-shape in the radial outer region of the grease chamber as a result of centrifugal force. Tests in this connection have shown that the amount of viscous medium for this purpose can be twice as much as that required for the speed-proportional damping. Therefore, the cost of the torsional vibration damper, as well as its weight, is increased unnecessarily.
A further problem in filling the grease chamber with a greater quantity of viscous medium is that viscous medium located in the toothing region is sprayed into a region located farther inward radially when the toothed wheels mesh with one another, wherein a seal in the above-mentioned region is intended to prevent the viscous medium from exiting the grease chamber. However, because of the radial proximity of the toothing location to the seal location and due to the high impact velocity of this sprayed grease, the seal does not have a sufficient operating reliability. A loss of viscous medium due to the insufficient seal results in increased toothing wear.